Page 161 - Photodetection and Measurement - Maximizing Performance in Optical Systems

Control of Ambient Light

154 Chapter Seven

1
0.8
Parallel
Transmission Perpendicular
Amplitude Coefficients 0.6 Perpendicular Reflection
0.4
Parallel
0.2
0.0
0.2
0.4
0.6
Refractive
0.8 indices: 1.0/1.5
1
0 10 20 30 40 50 60 70 80 90
Incidence Angle (°)

1
Intensity Reflection Coefficient 0.7 Perpendicular
0.9
0.8

0.6
0.5
0.4
0.3
Brewster's
angle
0.2
Parallel
0.1
0
0 10 20 30 40 50 60 70 80 90
Incidence Angle (°)
Figure 7.13 The amplitude and power reflection coefficients are given by
the Fresnel equations. At Brewster’s angle the reflection coefficient for
parallel-polarized light vanishes, giving a highly polarized reflection.

The intensities are obtained by squaring these amplitudes. The s and p corre-
spond to perpendicular and parallel electric vector polarizations respectively, 2
and 3 to the reflected and refracted amplitudes. Figure 7.13 shows the ampli-
tude and intensity reflection coefficients of glass for a range of angles.

7.5 Field of View Restriction, Absorption and
Mechanical Approaches

Next we come to mechanical screening techniques, at once trivial and complex.
This is primarily a question of knowing where interfering light sources are, and

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